SYSTEM: Late 2011 MacBook Pro 15" Mac OS X High Sierra beta Dual hard drives (1x SSD in main bay, 1x HDD in CD bay) PROBLEM: Can't boot past grey screen. Gets halfway through apple/progress bar screen (as above), then goes ALL grey and stays there. Might be connected to beta as i think it first started having issues after a particular update, but not sure how considering it affects more than OS X. I feel like I've ruled everything out. Everything works fine, it just won't boot to anything (os x, windows, usb installer, usb installation of OS X, etc) or let me boot off something else to reinstall the OS. I would think if it was logic board, i wouldn't be able to get as far as i do or run hardware test or get in single user mode right? SYMPTOMS: Normal Boot: Boots to apple logo/progress bar, gets halfway through, goes to grey screen stops there. Safe Boot: Boots to apple logo/progress bar, gets halfway through, goes to grey screen stops there. USB Boot: Boots to apple logo/progress bar, gets 1/2 - 3/4 through, goes to grey screen stops there. Verbose Boot: Gets through all text, goes to grey screen, stops Single User: No errors detected Windows 10: Gets past start up animation, goes to black screen, stops. FAILED REMEDIES: Safe Mode: No result (repeatedly) Local Recovery: Don't see any partition for recovery, don't think they do that anymore. Online Recovery: No result (repeatedly) Can start it, but it fails at same point. Reset NVRAM: No result (repeatedly) Reset PRAM: No result (repeatedly) New Battery: No result New AC adapter: No result New RAM: No result Boot from USB OS X: No result OS X USB Installer: No result Disconnect SSD: No result Disconnect HDD: No result Disconnect all HDs: No result Remove RAM1: No result Remove RAM2: No result New RAM 1/2: No result OTHER TESTS: check disk in SUM: error, but fixed, then no error Hardware Test: No errors except non-apple brand battery when swapping (hold D when starting) Extended Test: No errors WHAT WORKS: Power Light on front Startup chime Single user mode (text) display Can detect USB installer, all HDs and bootcamp All ports seem to work Fans Can power off battery or adapter Hardware Test mode (hold D while starting, NOT the regular OS X recovery/diagnostic mode) Hard drives seem to work, haven't been able to put in another computer yet will try that today. Not sure what else to try. Any constructive suggestion is welcome. Thank you if you read this far.